One-way, see-through panels are currently used in advertising, point of sale displays and other applications. Generally the panels are formed having an image which is viewable in one direction. The panels are perforated so that the perforations allow substantially unobstructed viewing through the panel in the opposite viewing direction. Common applications are advertising messages applied to the entire exterior surface of a bus so that viewers located exteriorly of the bus will be able to view the message or advertising image. Passengers within the bus have a substantially unobstructed view looking outwardly through the bus window.
Other typical applications are advertising applications such as store front windows, billboards or other transparent surfaces such as refrigerator case doors.
Typically, one-way panels are fabricated from a plastic film such as vinyl which carries a printed image and is visible when viewed from one direction and which appears substantially transparent when viewed from the opposite direction. The film has an opaque and a light-reflecting surface or coating.
U.K. Patent Application No. GB2118096 and U.S. Pat. No. 4,673,609 disclose similar one-way vision display panels which are fabricated from a substrate which comprises transparent, plastic sheets which are adhesively joined and which have a display image at the interface of two transparent panels of the assembly. In the panels of the above patent publications, the display image is visible when the panel assembly is viewed from one direction but is not seen when viewed from the opposite direction. In both instances, the display image is formed as pattern of opaque dots which are applied by screen, litho or a similar printing process to the panel interface. The opaque dots appear white or light in color on one side and black on the other. Light incident on the light colored side of the panel is scattered and reflected, thereby permitting an image formed by the dot pattern to be seen when viewed from this direction. Light incident on the opposite or black side of the panel is absorbed, such as the light is transmitted through the transparent portions of the panel permitting through-viewing in this direction.
It is also known to fabricate one-way vision display panels from metalized plastic film that is screen printed on one side and perforated with an ordered pattern of holes. The perforated, metalized film is then applied to the exterior surface of a window using either a double-sided tape or a spray adhesive.
U.S. Pat. No. 5,609,938 discloses one or more panels which define a support for an image layer and a relatively dark layer. Perforations extend through the panel and the layer. The perforations allow viewing through the panels in one direction without seeing the image yet the image can be viewed by looking through the panel assembly from the opposite.
Thus, the one-way, through-viewing effect can be achieved by a substrate which is either perforated or to which is applied a specific dot pattern or other pattern. For example, U.S. Pat. Nos. 4,925,705 and 4,673,609 disclose printed application of a dot or other patterns to achieve one-way visibility.
In addition, retroreflective material has been commonly employed for various safety, decorative and advertising purposes. Minnesota Mining and Manufacturing Company sells a product which is designated "Scotch Lite" and which relies upon small glass spheres embedded in a matrix of synthetic resin to provide retroreflectability. It would be desirable to provide one-way see-through substrates or image display panels as described above with retroreflectivity. However, there are inherent difficulties in doing this, particularly utilizing conventional retroreflective materials such as minute glass beads. As mentioned above, one-way panels are conventionally produced by perforating the laminate structure to provide holes or apertures which allow light passage so that substantial visibility and see-through capability is provided in one direction. Minute glass spheres embedded in the matrix of resin provide retroreflectivity but the application of such material to a one-way panel has problems in the perforation of the panels. Glass beads cannot be conventionally perforated by mechanical means as they will fracture. Further, glass beads are too abrasive for conventional tool and die perforating equipment.
Accordingly, to perforate a substrate of vinyl, plastic or other material which has one-way capability to which has been applied a material such as that sold under the trademark Scotch Lite requires complex and expensive perforation procedures. At present, the most practical way of perforating such a material is by means of laser which is expensive in first cost and expensive in operation and generally slow in operation. Laser perforating of material involves the use of a laser which has sufficient intensity to cut through the material and which are controlled by computers coupled to a servo motor. U.S. Pat. No. 5,550,346 discloses an apparatus of this type.
Accordingly, the present invention provides a one-way panel to which can be applied retroreflective surface over all or part of the panel and which panel can be perforated by conventional mechanical perforating means without the need or requirement of expensive computers or controlled servo lasers.